1. Field of the Invention
This invention relates to a process for breaking oil and water emulsions containing high molecular weight polymers and surfactants.
2. Prior Art
The following U.S. patents disclose various approaches to emulsion breaking and polymer degradation:
U.S. Pat. No. 1,515,093 to Crites et al teaches dehydrating oil by treating it with CaCl.sub.2 at a temperature of 140.degree. to 200.degree. F.
U.S. Pat. No. 2,064,541 to Hershman teaches desalting crude oil and breaking petroleum oil emulsions by treatment with a compound containing an --OCl group (e.g. sodium hypochlorite) and a peroxide.
U.S. Pat. No. 3,363,399 to Schmauch et al teaches purifying water contaminated with oil heavier than water by treatment with a de-emulsifying agent, preferably an electrolyte (e.g. calcium chloride).
U.S. Pat. Nos. 3,554,289, 3,684,015, 3,771,602 and 3,799,265 to Webb teach breaking hydrocarbon/water emulsions surrounding a wellbore by injecting a micellar dispersion to "solubilize" the emulsion.
U.S. Pat. No. 3,556,221 to Haws teaches reducing polymer plugging in a subterranean formation by injecting an aqueous solution having a pH of at least 8 and containing a compound of the formula MOX wherein M is an alkali metal or ammonium ion and X is a halogen (e.g. sodium hypochlorite).
Oil and water produced from oil-bearing subterranean formations by aqueous flooding, miscible flooding or other secondary recovery processes can contain significant amounts of oil and water emulsions. When these emulsions contain surfactant and high molecular weight polymer, they tend to be stable. The presence of surfactant facilitates both water retention in the lower density hydrocarbon phase and hydrocarbon emulsification in the aqueous phase. The presence of a high molecular weight polymer increases the viscosity of the aqueous phase, further compounding the problems of hydrocarbon/water phase separation. Since the hydrocarbon phase must be separated from the remainder of the emulsion before it can be efficiently refined, breaking of these emulsions becomes critical. Normal emulsion breaking techniques, e.g. settling in tanks, heat treatment, desalting, etc., are relatively inefficient, especially when considered within the economic framework of a large-scale production facility.